WHAT IS FACTOR V (LABILE FACTOR, PROACCELERIN, AC-GLOBULIN) TEST?
Factor V is a vitamin K–dependent glycoprotein synthesised in the liver. It is part of the prothrombin-converting complex that functions in the extrinsic pathway of blood clotting. Specifically, it is a cofactor that accelerates the conversion of prothrombin to thrombin. Factor V deficiency is an inherited, autosomal recessive condition that occurs with equal frequency in men and women. The symptoms can be mild to severe and include bruising easily, frequent nosebleeds, menorrhagia, and prolonged bleeding after traumatic episodes, including operative and dental procedures. One performs the test by first performing a prothrombin time (PT) on the client’s plasma. A factor V– deficient plasma substrate is then mixed with the client’s plasma, and the degree of correction in the PT is determined and compared to the degree of correction obtained by normal plasma. The Factor V Leiden mutation, newly identified in the 1990s, is a molecular defect in factor V, which makes it resistant to anticoagulant activation by protein C. The Leiden mutation is identified by performing an activated protein C resistance test and confirming an abnormal result with DNA evaluation for the Leiden mutation.